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Lê Quốc Trần Anh Coordinator

28/02/2018 at 15:23
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Find the last three-digit numbers of: \(M=2^{2018}\) 




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    Nguyễn Huy Thắng 28/04/2018 at 15:47

    We have: \(2^{2018}=\left(2^{1009}\right)^2=\left(2^{979}\cdot2^{30}\right)^2=\left(\left(2^{11}\right)^{89}\cdot2^{30}\right)^2\)

    \(\equiv\left(48^{89}\cdot824\right)^2\left(mod1000\right)\)\(=\left(48^3\cdot\left(48^2\right)^{43}\cdot824\right)^2\)

    \(\equiv\left(592\cdot304^{43}\cdot824\right)^2\left(mod1000\right)\)

    \(\equiv\left(592\cdot\left(304^5\right)^8\cdot464\cdot824\right)^2\left(mod1000\right)\)

    \(\equiv\left(912\cdot24^8\right)^2\left(mod1000\right)\)

    \(\equiv\left(912\cdot776^2\right)^2\left(mod1000\right)\)

    \(\equiv\left(912\cdot176\right)^2\left(mod1000\right)\)

    \(\equiv512^2\left(mod1000\right)\equiv144\left(mod1000\right)\)

    So the last three-digit numbers of \(M\) is \(144\)

    Lê Quốc Trần Anh selected this answer.
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    Đỗ Anh 10/05/2018 at 11:00

    Theo bài ra  ta có:  22018= ( 21009)2= ( 2979⋅ 230)2= ( ( 211)89⋅ 230)222018=(21009)2=(2979⋅230)2=((211)89⋅230)2

    ≡ ( 4889⋅ 824 )2( m o d1000 )≡(4889⋅824)2(mod1000)= ( 483⋅ ( 482)43⋅ 824 )2=(483⋅(482)43⋅824)2

    ≡ ( 592 ⋅ 30443⋅ 824 )2( m o d1000 )≡(592⋅30443⋅824)2(mod1000)

    ≡ ( 592 ⋅ ( 3045)số 8⋅ 464 ⋅ 824 )2( m o d1000 )≡(592⋅(3045)số 8⋅464⋅824)2(mod1000)

    ≡ ( 912 ⋅ 24số 8)2( m o d1000 )≡(912⋅24số 8)2(mod1000)

    ≡ ( 912 ⋅ 7762)2( m o d1000 )≡(912⋅7762)2(mod1000)

    ≡ ( 912 ⋅ 176 )2( m o d1000 )≡(912⋅176)2(mod1000)

    ≡ 5122( m o d1000 ) ≡144 ( m o d1000 )≡5122(mod1000)≡144(mod1000)

    Vì vậy, con số ba chữ số cuối cùng của  MM  là  144


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